Brake fluid transfer from Master pump to ABS pump

Not sure of the model EX, but it probably has a clutch hydraulic slave and master cylinder that has leaked out the hydraulic fluid. Fill the clutch master cylinder (near the brake master cylinder) with brake fluid and pump the clutch pedal several times. The clutch work again until the fluid leaks out, so the permanent fix is to replace the master and or slave cylinders and bleed the system. Other models have a clutch cable that would need replacing in this case

Honda had two brake reservoirs one on the normal brake master cylinder the other on the ABS module. If abs fuse has no power the module has no power. that power comes from the main fuses in underhood fuse box. the abs system is supplement system to normal braking system loss of brake pedal is a air problem or drum brake adjustment problem or a loose wheel bearing pushing the caliper piston back into caliper requiring more fluid to get brake to work causing a low pedal.

Let's look at your slave cylinder and your master cylinder.
Under the hood of your car are two master cylinders, and physically, they are close together.
They are found right in front of you as you drive the car, except they are under the hood and about chest high.
My 1990 has them right along side one another.
The brake master cylinder reservoir is about 4 inches in diameter, the clutch master cylinder reservoir is about 3 inches in diameter. Both of them take quality brake fluid.
Sounds like your clutch master cylinder is dry of brake fluid.
It would be nice if all you had to do was to add brake fluid to the "fill" line, but then you'd have air in that system, and it would need to be "bled" to work.
If you do find the brake fluid low, very likely the slave cylinder needs replacement, as your car is the right age to need this.
Be blessed.

solve the problem by replace or rebuild the master cylinder. This happens over time.

Short of jacking up the wheel and putting a new car underneath, you've just about covered all the possibilities. But I wonder, perhaps in your attempts to solve this, if you have inadvertantly introduced another fault? As you know, the brake master cylinder on a disc braked vehicle has no static valve. If there were to be a static valve in the master cylinder, the brakes would lock on after a few pumps. But this would affect both front wheels. There could also be a collapsed section in one of the flexible hoses which would let fluid through for bleeding but not allow the fluid to return. this would hold the brake on too. When you had the cliper off, did the rotor trun freely?

There may be air in the lines. Bleed all your brakes starting at the farthest wheel from the resevoir, and finishing at the closest one. Try the pedal after its bled. If the pedal still feels soft or travels to the floor there may be a pinhole leak that may be spraying on the underbody of the car, or the seals in the master cylinder are gone filling the vacuum booster(if equipped). Air compresses more than oil so if bleeding works that may be the problem.

You need to bleed them well..
Open the master cap.. Open the bleed valve on each break and let the fluid run out NOT letting the master empty all the way..
Run a few pints through and tighten everything up and you should be good to go..

first thing to check is your fluid level. ensure you have enough fluid in your master cylinder. it sounds like you have air in the system. its not really hard to bleed. just get a friend to come over and one of you climb under the car with a bucket and a wrench and some rags. open the bleeder valve on the calipers and have your buddy press the pedal. once oil shoots out straight from the valve close it while its still squirting. if the oil has alot of air in it have your buddy keep pumping to until its not. also make sure you watch your master cylinder level as you are just squirting it all out. do that to all the brakes. as far as it being the master cylinder thats a way later thing. you check the fluid level/air in lines first. as far as the abs. is your abs light on? problem with abs is that it requires specialized work so your best bet is taking it to a shop. but if there isnt air in the lines and there is plenty of fluid then start looking at your brake adjustment. if that is good then possibly the master or slave cylinder

Likely one of the wheel sensors. Check that the master cylinder reservoir and ABS unit have enough brake fluid. When the light is on, ABS is disabled, the brakes should continue to work just like a car without ABS.

Do you still have the problem ? If so, try disabling the ABS completely (electrically) by disconnecting the 50 amp breaker and remove the ABS controller. You should have brake power restored and be careful as the brakes will lock now if you apply too much foot pedal pressure. I hope this helps.